It is known to effect automatic control of a vehicle with a view to causing the vehicle to follow a desired track the defining parameters of which have been previously memorised. Such control may be implemented on an optimal control basis in which the control process is effected in a manner optimising a performance criterion; typically, this performance criterion might be a function of the vehicle track error (that is, the error between the desired track and the vehicle's actual track) the control process being designed to minimise the value of the performance criterion.
The application of optimal control theory to ships has, in the past, been primarily in relation to fuel conservation in large vessels and comparatively little research and development effort has been put into the problem and automatic track keeping. One recent paper that does deal with automatic track keeping for ships was presented in October 1982 at a conference held at the Royal Naval Engineering College, Manadon, Plymouth, England, this paper being part-authored by the present inventors and being entitled "Automatic Pilotage of Large Ships in Confined Waters--A Multivariable Approach". The paper sets out in clear mathematical terms the general nature of an optimal control process to which the present invention may be applied.
In implementing automatic pilotage of a vessel, an important consideration is how best to effect a change over between following one segment of the desired track to following a subsequent segment having a different heading.
It is an object of the present invention to facilitate the implementation of changes in track in an automatic pilotage system based on an optimal control process such as described in the above-mentioned Paper.